<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>>for test</title>
    </head>
    <body>
        <div id="descr">

        </div>
        <div id="app">
            <h1>{{ message }}</h1>
            <button type="button" @click="changeCounter()">Click</button>
        </div>
        <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
        <script>
            var app = new Vue({
                el: '#app',
                data: {
                    counter: 1
                },
                computed: {
                    message: function() {
                        return this.counter + 1;
                    }
                },
                watch: {
                    message: function(val) {
                        this.counter = this.counter + 1;
                    }
                },
                methods: {
                    changeCounter: function() {
                        this.counter = 2;
                    }
                }
            })
        </script>
    </body>
</html>